Prehung doors will ship knocked down to avoid damages and to ease the handling. These doors have been machined and the prep work finished, but none of the individual parts have been applied. A knocked down door can be put together into an assembled door in about 10 minutes.

Generally an exterior wood doors can perform well if properly protected and maintained.
Manufacturer require adequate overhang to protect the door from excessive sunlight and rain and also suggest to fully finish the doors to increase its durability. There is no information from the manufacturer to suggest against Midwest area.
Please read the warranty for the limits of use.